Because he is best known as water conservationist who got Nobel Peace prize too for it. He is from Alwar, Rajasthan, India. So, Rajendra Singh is considered as Water man of India.
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Because He is a water conservationist. He won the Stockholm Water Prize, an award known as "the Nobel Prize for water", in 2015. Previously, he won the Ramon Magsaysay Award for community leadership in 2001 for his pioneering work in community-based efforts in water harvesting and water management.